truck over reved today?

was on my way home from work about 1 mile from work my truck seemed to over rev jumped from 3500 to 4000 rpms real quick it seemed like then upto 5000 really fast w/o giving anymore throttle. turned around and went back to work and looked under the hood and found a sharp pointed rubber stopper on one end and a round threaded on other end object on other end in a slotted hole where the air box would be sitting if i didnt have an intake. thought it just might have got sucked up against the air filter. it made a sound kind of like a hose was loose or something. sucking air or something. the sucking sound is gone but still kinda seems to rev up funny at 3500 rpms. the check engine light came on last week and i took to o'reillys to have tested and they said it was a bad o2 sensor but i asked if it could be b/c i had put the intake on like 2 weeks earlier or puttin the exhaust on like a month and a half before and they said it could be so just had it reset and has not come back on since. today the change oil light came on after i turned the engine off after the over reving and it is time for an oil change (about 4000 miles) gonna change it tomorrow and check the tranny fluid. does anybody have any opinions on the over reving or is it just in my head? the wind was blowing really hard today it could have just been it and the rubber stopper could have blown off the road or something. also just replace the alternator b/c it was goin bad and the pulley next to it and the belt b/c the bearings being thrown from the alternator or the pulley one wore the belt.

Sounds to me like the piece that holds the lower air box to the fender well. May have come out of the air box and sucked up. Pull the filter out and look if there is a hole in the bottom of the air box and a slotted piece under the air box. That's where that piece may fit. That would give an air sucking sound, but I wouldn't think that would cause the over rev. Did the computer shut the truck down once it passed 4k rpm?